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-The relationship between the number of Paenibacillus larvae larvae spores fed individually to 24-28, 48-52 and 72-76 h old Apis mellifera ligustica larvae and the number of larvae dying from the P. l. larvae infection was investigated as well as the effect of sublethal infection with P. l. larvae on larval development time and adult weight. The larvae were laboratory reared, thus, excluding the influence of nurse bees. The results show that larvae 24-28 h old are most susceptible to infection with P. l. larvae with a clear dose-response relationship (LD 50 = 8.49). Older larvae become more and more resistant to infection with P. l. larvae so that no significant dose-mortality relationship exists in the 48-52 and 72-76 h age groups. Furthermore, a significant negative correlation exists between the development time and emergence weight for the adult bees in both the non-inoculated group and the inoculated group. There was no difference in development time between non-inoculated larvae and those that survived the inoculation. © Inra/DIB/AGIB/Elsevier, Paris Apis mellifera ligustica / American foulbrood / Paenibacillus larvae larvae / LD 50 / in vitro rearing

-An environmental concern regarding the cultivation of transgenic crop plants is their effect on non-target organisms. Honey bees are obvious non-target arthropods to be included in a risk assessment procedure but due to their complex social behaviour, testing transgene products on individual bees is not possible in bee colonies. We employed a laboratory larval rearing technique to test the impacts of such transgene products on honey bees. A serine proteinase inhibitor (Kunitz Soybean Trypsin Inhibitor, SBTI), that is a source of insect resistance in transgenic plants, was used as a model insecticidal protein on honey bee larvae reared individually in the laboratory. The addition of 1.0% SBTI (w:w of total protein) to the larval diet created significant additional larval mortality, slowed juvenile development and significantly decreased adult body mass. Our results suggest that the larval rearing technique can be used to monitor direct side-effects of transgene products on individual honey bee larvae.Apis mellifera / risk assessment / larval rearing / transgenic plants / proteinase inhibitor

The mortality of honey bee larvae and pupae reared in vitro caused by various combinations of oral inoculation with Paenibacillus larvae larvae spores, acute paralysis virus (APV), and infestation with Varroa jacobsoni was studied. The effect of the mite itself and the mite acting as a vector of APV on the mortality of larvae and pupae was investigated. Mortality caused by P. l. larvae ranged from 25 to 55% depending on spore dose. Oral inoculation with APV caused 9% mortality, which was not additive to the mortality caused by P. l. larvae. P. l. larvae did not induce the activation of APV infection. The mortality caused by V. jacobsoni itself was 25%, and by mites transmitting APV, 55%. Neither the mites themselves or the mites transmitting APV had an additive effect on mortality caused by P. l. larvae. The study suggests that APV transmitted by mites is the most significant cause of mortality of the treatment combinations tested. The results do not suggest that the mite itself or the mites transmitting APV act as a stress factor provoking clinical symptoms of American foulbrood (AFB) in individual larvae in the in vitro rearing system.

A pollination experiment was conducted with Parkia biglobosa (Fabaceae) in The Gambia. P. biglobosa is integrated in the farming systems and produces fruit pulp and seeds used in cooking. The species is bat-pollinated, and in areas with few bats the main pollinators are assumed to be honey bees. A higher rate of effective pollination will in many instances increase fruit production, and the aim of this study was to investigate pollination efficiency of different pollinators. Access of flower visiting animals to flowers was controlled by nets with differently sized mesh, using five trees as replicates. The pollinators' identity, efficiency, and relative effect were determined. Bats, honey bees, and stingless bees were able to pollinate the species. Bat-visited capitula produced more pods, but not significantly more than honey bees. Honey bees were more efficient than stingless bees, resulting in significantly less aborted seeds. The treatment which excluded all flower visitors developed no mature pods, indicating that P. biglobosa was not autonomous autogamous, apomictic, or parthenocarpic, while the treatment with confined honey bees showed that geitonogamy is possible. Sugar content of fruit pulp was analysed and a positive correlation between number of seeds per pod and the sugar content was found. Improved pollination success may thus result in sweeter fruits. We conclude it is important to strive against a pollinator-friendly environment in order to attract bats and bees. Furthermore, we suggest beekeeping in the vicinity of P. biglobosa as a way to increase yield.

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The activities of two detoxification enzymes, glutathione S-transferase (GST) with 1-chloro-2,4-dinitrobenzene (CDNB) as substrate, and glutathione peroxidase with tert-butyl hydroperoxide as substrate (GSH-Px[TBH]), were measured in the larvae, pupae and adults of honey bees (Apis mellifera ligustica Spinola) originating from two colonies, one untreated acting as a control group and the other treated with flumethrin. The treatment with flumethrin led to increased GST activity in the larval instars, pupae and nurse bees compared with the control group. In particular, the late fifth larval instars (LS) and the pupal instars showed increased GST activities. GSH-Px[TBH] activities were highest in the early larval instars (L1–L2). Treatment with flumethrin resulted in the induction of GSH-Px[TBH] activity in the L4–L5 instars and LS. In the forager bees, the enzyme activity was lower in the group treated with flumethrin than in the control group. This could have been due to unknown extrinsic environmental factors. In general, the average protein contents were lower in the flumethrin-treated group than in the control group. In the LS and pupal stage, and in the adult worker bees, the differences were significantly lower. This inhibition of growth could be due to metabolic costs resulting from exposure to toxicants.

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